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Sodium fluorescein as a retinal pH indicator?
Martin Hammer1, Dietrich Schweitzer, Sandra Richter
1Department of Ophthalmology, University of Jena, Bachstr. 18, 07740 Jena, Germany. martin.hammer@med.uni-jena.de
Physiological Measurement
|May 12, 2005
Summary
Sodium fluorescein can indicate retinal acidosis by measuring its fluorescence lifetime. This method detects hypoxic fundus areas early, aiding in the treatment of eye diseases before visible changes occur.
Area of Science:
- Ophthalmology
- Biomedical Optics
- Biochemistry
Background:
- Retinal neovascularization, often linked to hypoxia and acidosis, is a key manifestation of various eye diseases.
- Early detection of hypoxic fundus areas could enable timely treatment before vascular changes appear.
Purpose of the Study:
- To investigate sodium fluorescein as a potential indicator of retinal pH.
- To determine if fluorescence lifetime measurements can detect acidosis in the retina.
Main Methods:
- Sodium fluorescein solutions were tested across a pH range of 6.5 to 8.6.
- Fluorescence lifetime was measured using time-correlated single photon counting (TCSPC) excited by a pulsed diode laser.
- The influence of temperature and sodium fluorescein concentration on fluorescence lifetime was assessed.
Main Results:
- Fluorescence lifetime increased from 3.775 ns to 4.11 ns as pH rose from 6.5 to 8.6.
- Significant pH-dependent changes in fluorescence lifetime were observed (P<0.0005 at pH<7.65, P≤0.02 at pH>7.65).
- Fluorescence lifetime was independent of temperature (22-37°C) and sodium fluorescein concentration.
Conclusions:
- Sodium fluorescein's fluorescence lifetime is a reliable indicator of pH, unaffected by temperature or concentration.
- Combining TCSPC with scanning laser ophthalmoscopy may allow for the detection of retinal acidosis.
- Further in vivo studies are needed to confirm the accuracy of this technique in the human fundus.